Heat treating apparatus



1942. G. H. BROWN HEAT TREATING APPARATUS Filed May 31, 1941 2Sheets-Sheet l lugkwkm (Zttorneg Dec. 1, 1942.

G. H. BROWN -HEAT TREATING APPARAT u Filed May 51, 1941 v g 39 J7 T IL T77 3/ Z9 Imventor v Gwyn/553M107 Patented Dec. 1, 1942 HEAT TREATINGAPPARATUS George H. Brown, Haddoniield, N. J., assignor to RadioCorporation of America, a corporation of Delaware Application May 31,1941, Serial No. 396,102

10 Claims.

This invention relates to heat treating apparatus, and more particularlyto apparatus employing an electrostatic field for heating materials ofhigh resistance, the present invention being particularly useful inconnection with, although by no means limited to, the heating of rayonthreads in the manufacture thereof.

Under certain circumstances, it has been found desirable to apply heatto rayon threads in the course of fabricating the threads. Th conditionsunder which rayon is manufactured make it rather diflicult to apply heatto the threads by conventional methods, and the primary object of mypresent invention is to provide an improved heating method and apparatuswhich will be suitable for this purpose.

More particularly, it is an object of my present invention to provide animproved method of heating a thread, wire, strip or the like of highresistance in a manner which is both simple and economical, as well ashighly eflicient.

In accordance with this invention, I provide a high frequency oscillatorwhich may be designed to generate alternating current of a frequency ofthe order of between ten and fifteen megacycles. Included in theoscillator are a plurality of terminal electrodes maintained atdifferent potentials and disposed in spaced relation to each other alonga predetermined path. As the rayon thread, is brought out from thesulphuric acid bath, in which the threads are solidified, they areadvanced along said path successively past said terminals or electrodesand in closely spaced relation thereto so as to be capacitlvely coupledto -the electrodes. Thus, as the thread passes these electrodes, analternating current of high frequency is caused to flow therein, andthis current heats the portion of the rayon threads between theelectrodes, the rayon having, of

course, been rendered conductive by the sulphuric acid. i

slightly difierent form of my invention which may be used in a systemsuch as that shown in Figure 1,

Figure 3 is a wiring diagram corresponding to Figure 2 and showing theelectrical analogues of certain parts shown structurally in Figure 2,

Figure 4 is a schematic diagram showing still another form of myinvention which may be used in a system such as that shown in Figure l,and

Figure 5 is a wiring diagram corresponding to Figure 4 and showing theelectrical analogues of certain parts shown structurally in Figure 4.

Referring more particularly to the drawings, wherein similar referencecharacters designate corresponding parts throughout, there is shown, inFig. l, a storage tank I for the liquid viscose from which the rayon ismade and a pump 3 which serves to force the liquid in the tank I througha pipe '5 which terminates in a perforated plate in the side of a tank 1containing sulphuric acid. As the liquid material is forced through theopenings in the aforementioned perforated plate, it is formed into thinthreads which solidify as soon as they come in contact with i thesulphuric acid. From the tank I, the threads 9 (of which only one isshown in the drawing for the sake of simplicity) pass around a pluralityof rollers H), H, I3, l5 and I1 and are fed into a cylindrical drum ortank IS on a turntable 2| which is driven by a motor 23, the thread 9collecting in spiral fashion in the drum I9.

The roller I1 is preferably driven at a greater speed than the roller l5whereby the thread 9 is caused to stretch between these two rollers. Itis between the rollers l5 and I! that it has been found desirable toalso apply heat to the stretched threads. For this purpose, I provide,according to the form of my invention shown in Fig. 1, an oscillator 2-5which includes a pair of vacuum tubes 21 and 29 arranged in push-pullrelation and a tuned tank circuit 3|, having an inductance 33 and acapacitance 34 in shunt relation. The inductance 33 constitutes theprimary winding of an output transformer 35 having a secondary winding31 in series with an inductance 39 which is tuned to the desiredfrequency with a capacitance 4 l.

Spaced from each other along the path 01' movement of the thread 9between the rollers I5 and I! are three cooperating electrodes orterminals for the oscillator 25. The end terminals 43 and 45 areconnected to a grounded conductive plate 41 and are therefore maintainedat ground potential. Intermediate the electrodes 43 and 45 is a thirdelectrode 49 supported on the plate 41 from which it is insulated by aninsulator 5|, the electrode or terminal 49 being spaced substantiallyequally from each of the terminals 43 and 45. One side of the outputcircuit of the oscillator 25 may be connected to ground (through theterminal 45, for example) by a lead 53, and the other side of the outputcircuit is connected to the terminal or electrode 49 by a lead 55. Theelectrodes 43, 45 and 49 are preferably V shaped in cross-section andare disposed in aligned relation with each other, the thread 9 beingarranged to pass between the sides of the V's but in spaced relation totheir vertices, as well as the sides thereof. Thus, it will be obviousthat the conductive portion of the thread 9 is capacitively coupled toeach of the electrodes 43, 49 and 45 as it passes along them insuccession.

The oscillator 25 preferably operates at a frequency of between 10 andmegacycles and generates voltages which set up electric fields aroundthe electrodes. By reason of the-capacitive coupling between the thread9 and the several electrodes, an alternating current of correspondinglyhigh frequency is caused to fiow in the thread 9 between the electrodes43 and 49 as one pair and the electrodes 45 and 49 as another pair, thecurrent fiowing in that portion of the thread 9 between the electrodes43 and 49 being first in one direction (for example, in the direction oftravel of the thread 9) and then in the opposite direction, and thecurrent flowing in that portion of the thread 9 between the electrodes45 and 49 being simultaneously first in said opposite direction and thenin the direction of travel of the thread. The current fiowing in thethread 9 generates heat therein while the thread is being stretchedbetween the rollers l5 and I1.

In Fig. 2, there is shown an oscillator which employs only twoelectrodes 51 and 59, the lead 53 being connected to the electrode 51and the lead 55 being connected to the electrode 59. In all otherrespects, the oscillator of Fig. 2 may be similar to that shown in Fig.1.

Fig. 3 illustrates the action of the system shown in Fig. 2. In Fig. 3,the capacitor Bl represents the capacity between the electrode 51 andthe thread 9 of Fig. 2, the capacitor 63 represents the capacity betweenthe electrode 59 andthe thread 9, and the resistance 65 represents theresistance of that portion of the thread 9 through which current flows(that is, the portion of the thread between the electrodes or terminals51 and 59). It is due to the resistance 65 that the requisite heat isgenerated by the high frequency alternating current flowing in thethread 9.

Fig. 4 shows an oscillator similar to that shown in Fig. l, but includedin series with the lead 55 and the middle electrode 49 is a tunablecircuit constituted by an inductance 51 and a variable capacitor 69 forfurther controlling the operating frequency of the oscillator.

Fig. 5 shows more clearly the operation of the system of Fig. 4, thecapacitor ll of Fig. 5 representing the capacity between the electrodeor terminal 43 and the thread 9, the capacitor-13 representing thecapacitance between the electrode or terminal 45 and the thread 9, andthe capacitor 15 representing the capacitance between the intermediateelectrode or terminal 49 and the thread 9. The resistance 11 shown inFig. 5 represents the resistance of the portion of the thread 9 which isbetween the electrodes 43 and 49, and the resistance 19 of Fig. 5represents the resistance of that portion of the thread 9 which isbetween the electrodes and 49, it being apparent from an inspection ofFig. 5 that current will fiow in each of the resistances I1 and 19 inopposite directions.

Although I have shown and described several embodiments of my invention,it will be apparent to those skilled in the art that many othervariations thereof are possible. For example, any

other suitable type of oscillator than those shown may be employed; theelectrodes 43, 45 and 49 may be of any other suitable shape than a V;any suitable number of pairs of cooperating electrodes may be employed,and so on. Also, it will undoubtedly be apparent to those skilled in theart that my invention is not necessarily limited to use in connectionwith the heating of rayon thread, but that it may be used equally wellfor heating any high resistance conductive strip, web, film, or thelike, such as high resistance wire, or tape, the strip or the like beingfirst rendered conductive where it is normally nonconductive. Since myinvention is capable of a variety of expressions and uses, I desire tohave it understood that I do not wish to limit myself except insofar asis made necessary by the prior art and by the spirit of the appendedclaims.

I claim as my invention:

1. The method of treating a strip of electroconductive material whichcomprises moving said strip along a predetermined path, applying to saidstrip capacitively a high frequency alternating current as it passesalong said path whereby to effect heating thereof, and simultaneouslycausing said strip to stretch as it passes along at least a portion ofsaid path.

2. The method of treating a strip of electroconductive material whichcomprises moving said strip along a predetermined path, establishingelectric fields at spaced points along said path, causing said electricfields to vary at a high frequency, passing said strip successivelythrough said fields to thereby cause a fiow of current in said stripfrom one of said fields to another of said fields to thereby heat saidstrip, and simultaneously causing said strip to stretch as it passesbetween said points.

3. The method of treating a strip of conductive material which comprisesmoving said strip along a predetermined path, establishing two electricfields of different polarity at spaced points along said path, causingthe polarity of said fields to reverse at a high frequency, passing saidstrip successively through said fields to thereby cause an alternatingcurrent of high frequency to fiow in said strip between said points tothereby heat said strip, and simultaneously causing said strip tostretch as it passes between said points.

4. The method of treating a strip of electroconductive material whichcomprises passing said strip along a predetermined path, generating inan oscillatory circuit which has terminals at spaced points in said patha high frequency alternating current, passing said strip successivelypast said terminals in capacitive relation thereto whereby to generate acurrent in the portions of said strip between said terminals for heatingsaid portion, and simultaneously causing said strip to stretch as itpasses between said terminals.

5. The method of treating a strip of electroconductive material whichcomprises passing said strip along a predetermined path and in apredetermined direction, generating in an osclllatory circuit which hasterminals at spaced points in said path a high frequency alternatingcurrent, passing said strip successively past said terminals incapacitive relation thereto whereby to generate in the portion of saidstrip between said terminals an alternating current which flows throughsaid strip alternately in the direction of travel thereof and then inthe opposite direction for heating said portion, and simultaneouslycausing said strip to stretch as it passes between said terminals.

6. The method of treating a strip of electroconductive material whichcomprises passing said strip along a predetermined path and in apredetermined direction, generating a high frequency alternating currentin an oscillatory circuit which has a pair of terminals of one potentialat spaced points along said path and a third terminal in said pathintermediate said first named terminals at a different potential,passing said strip successively past said three terminals in capacitiverelation thereto whereby to generate in the portion of said stripbetween one of said first named two terminals and said intermediateterminal an alternating current which fiows through said portionalternately first in said predetermined direction and then in theopposite direction and simultaneously to generate in the portion of saidstrip between said inter- -mediate terminal and the other of said firstnamed two terminals an alternating current which flows through said lastnamed strip portion alternately first in said opposite direction andthen in said predetermined direction for heating both said stripportions and simultaneously causing said strip to stretch as it passesbetween said first named pair of terminals.

7. In a system for treating a movable conductive strip, the combinationof a high irequency oscillator including a plurality of cooperativelyassociated terminals in spaced relation to each other along apredetermined path, means for moving said strip along said pathsuccessively past said terminals and in slightly spaced relation to saidterminals whereby said strip is capacitively coupled to said terminalsas it passes by them, and constitutes a current path therebetween, andmeans for simultaneously stretching the portion of said strip betweensaid terminals as it moves therebetween.

8. In a system for treating a movable conductive strip, the combinationof a high frequency oscillator including a pair of terminals in spacedrelation to each other along a predetermined path and a third terminalin said path intermediate said two first named terminals, means formaintaining said first named two terminals at a predetermined potential,means for varying the potential of said third terminal relative to saidfirst named two terminals at a high frequency, and means for moving saidstrip along said path successively past said three terminals in slightlyspaced relation thereto whereby said strip is capacitively coupled tosaid terminals as it passes them to thereby generate in said stripalternating current for heating said strip.

9. The invention set forth in claim 7 characterized in that saidterminals are constituted by substantially V-shaped electrodes andcharacterized further in that said electrodes and said strip are sodisposed in said path that said strip passes between the sides of eachof said electrodes and in proximity to the apex thereof.

10. In the method of forming rayon by coagulation of viscose material bymeans of an electroconductive coagulating material, the steps whichcomprise forming the viscose material into a thread, coagulating saidthread with said conductive material whereby to render said threadelectro-conductive, moving said electro-conductive thread continuouslyalong a predetermined path, generating in an oscillatory circuit whichhas terminals at spaced oints in said path a high frequency alternatingcurrent, and passing said electro-conductive thread successively pastsaid terminals in capacitive relation thereto whereby to generate inthat portion of said thread which lies between said terminals at anytime a current for heating said thread portion.

GEORGE H. BROWN.

